Cohen-Tannoudji, Claude (1933– )

French physicist who with US physicists William D Phillips and Steven Chu was awarded the Nobel Prize for Physics in 1997 for the development of techniques using laser light to cool and trap atoms to extremely low temperatures.

Atoms and molecules in the air move at around 4,000 km/2,490 m per hour. Chu and Phillips had developed techniques using lasers which were capable of cooling atoms and molecules to temperatures within a fraction of a degree of absolute zero, or zero degrees kelvin, −273.15°C/−459.67°F. This reduced the speed of an atom to less than 1 km per hour/0.6 mi per hour. In 1988, Phillips succeeded in achieving a temperature of 0.00004 kelvin. However this temperature was six times lower than was possible if the theory he had been using was correct. Cohen-Tannoudji successfully accounted for the errors in the theory used by Chu and Phillips and developed more advanced methods of cooling atoms using laser techniques. In 1995 his research group cooled helium atoms to within eighteen millionths of a degree of absolute zero, at which temperature the atoms were only moving at less than 2 cm per second/0.8 in per second. The techniques developed by Chu, Phillips, and Cohen-Tannoudji have helped in the understanding of how matter and light interact and have provided a tool for the study of individual atoms and molecules.

Cohen-Tannoudji was born in Constantine, Algeria, and is a French citizen. He received his PhD in physics from the Ecole Normale Supérieure (ENS), Paris, France, in 1962, where he became a research scientist in the physics department. He divided his time between research and teaching. While carrying out research at ENS, he taught physics at the University of Paris VI from 1964 until 1973, when he became a professor at the Collège de France.